TacView is a third party program that records flight/telemetry information about every vehicle in a mission, and features a playback engine to allow you to get a "godmode" view of every event that occurred during a mission. TacView is enormously useful because it allows you to review your played missions from the "godmode" perspective, which allows you to determine what went wrong or right during your flights: if you for example think you just died out of nothing, TacView can help you by reviewing your 'track' (a recording of your flight) and for example tell you it was that sneaky Russian SU-27 that killed you with a heatseeker.
From their site:
"Eager to understand what really happened during your last flight? Tacview is a universal flight data analysis tool which enables you to easily record, analyze and understand any flight to improve your skills much faster than with conventional debriefings."
Tacview's official site has detailed information about installing TacView for a variety of different sim (it also works for X-Plane, Falcon 4, and a handful of others!).
Tacview's DCS installation guide will get you setup, single player setup is relatively simple, if you plan on hosting multiplayer servers make sure you read that link thoroughly to ensure that other players can record their data when flying on your server.